Impact of eco-friendly treatments on managing onion downy mildew

Onion (Allium cepa L.) is a significant agricultural crop in Egypt, valued for their contributions to both domestic consumption and export markets. However, onion cultivation faces considerable challenges, notably from downy mildew, caused by Peronospora destructor (Berk.) Casp. Serenade ASO 1.34% SC (Bacillus subtilis QST 713 1x109 cfu/g) and Tricho Nitro Plus WP (Trichoderma spp. 107 spores/ml) were applied at a concentration of 1 L/100 L water/feddan, while Bio Control T34 12% WP (Trichoderma asperellum 107 spores/g) and Champ DP 57.6% WG, a copper hydroxide-based fungicide were applied at a concentration of 85 and 180 g/100 L water/feddan respectively to study their effect on onion downy mildew. Champ DP emerging as the most effective solution, significantly reducing the severity of disease by 80.3% and 76.4% after two and three months of application during the 2022-23 and 2023-24 growing seasons. Tricho Nitro Plus followed closely, demonstrating a reduction of 80.2% and 76.3% in disease severity, highlighting its potential as an effective biocide. Notably, all treatments resulted in increasing in onion bulbs yield and enhanced total carbohydrate, total soluble solids and plant enzymes defenses. In conclusion, the application of all treatments, particularly Champ DP and Tricho Nitro Plus, significantly mitigates onion downy mildew, thereby enhancing the yield and quality. This research underscores the potential of integrated management approaches that combine chemical and biological treatments to sustainably address the challenges posed by plant pathogens in onion cultivation, fostering both local food security and agricultural export opportunities in Egypt.